Exposure apparatus for electrophotographic reproduction machines

ABSTRACT

The machine includes a setting device for adjusting the exposure from a normal exposure, a programming mechanism for single or multiple copying operations and including a device for signalling the end of a single or multiple copying operation, and a resetting device for automatically returning the setting device to a setting for normal exposure in response to the signal from the programming mechanism. Additionally and in another embodiment, the machine includes a timing device which retards actuation of the resetting device for a period that is slightly longer than the time required to change from one original to another.

United States Patent [191 Moser 1 Nov. 13, 1973 [54] EXPOSURE APPARATUS FOR 3,602,579 8/1971 Silvertooth 355/36 x ELECTROPHOTOGRAPHIC REPRODUCTION MACHINES FOREIGN PATENTS OR APPEICATIONS 1,292,000 4/1969 Germany 355/3 ux Hermann Moser, 38, Wilhelm-Glassing-Strasse, Darmstadt, Germany Filed: Oct. 2, 1972 Appl. No.: 293,838

Inventor:

Foreign Application Priority Data Oct. 4, 1971 Germany P 21 49 404.2

U.S. Cl. 355/14, 355/3, 355/67, 355/71 Int. Cl. G03b 27/54, G03g 15/00 Field of Search 355/14, 3, 67, 71, 355/35, 36; 350/269 References Cited UNITED STATES PATENTS 10/1963 Engelage 355/36 Primary Examiner-Robert P. Greiner Attorney-Robert E Le Blanc et a1.

[57] ABSTRACT The machine includes a setting device for adjusting the exposure from a normal exposure, a programming mechanism for single or multiple copying operations and including a device for signalling the end of a single or multiple copying operation, and a resetting device for automatically returning the setting device to a setting for normal exposure in response to the signal from the programming mechanism. Additionally and in another embodiment, the machine includes a timing device which retards actuation of the resetting device for a period that is slightly longer than the time re quired to change from one original to another.

11 Claims, 1 Drawing Figure EXPOSURE APPARATUS FOR ELECTROPHOTOGRAPHIC REPRODUCTION MACHINES This invention concerns apparatus for adjusting exposure in an electrophotographic reproduction machine.

In electrophotographic reproduction machines it is necessary to vary the exposure at will in order always to obtain copies of substantially equal richness in contrast even when the originals deviate from the normal contrast, for example, of a printed page. This can be done in a particularly simple manner in the case of a machine using slit exposure. In this case the width of the slit can be adjusted.

However, apparatus of this type suffers from the disadvantage that an adjusted exposure deviating from the normal exposure is maintained when the original is changed. This has a particularly troublesome effect when different people use the reproduction machine one .after another.

It has been proposed in German Pat. Specification No. 1,292,000, as published, to provide a resetting device which is automatically actuated upon completion of the travel of a copy through the machine. This device suffers from the disadvantage that, in certain circumstances, exposure has to be adjusted again after each copy has been made. Thus, this device is unsuitable particularly for use with high speed copying machines which are intended for producing several copies from one original.

The present invention provides, in an electrophotographic reproduction machine, an apparatus for adjusting the exposure, said apparatus comprising a setting device for setting the period and/or intensity of exposure over a range including a setting for normal exposure, and an electrically releasable resetting device for returning the setting device to the said setting for normal exposure after it has been set at any other setting, the electrical release means for said resetting device being so adapted for cooperation with a mechanism of the machine for programming to a single or multiple copying operation that on running down of said mechanism at the end of said copying operation, the release means is caused to release the resetting device.

The apparatus of the invention offers the advantage that, upon completion of a single or multiple copying operation as programmed by the machine, the normal exposure is automatically reset. It is not necessary in the case of a multiple copyingoperation to reset'or maintain the adjusted exposure each time. Instead, the machine is only reset to normal exposure upon completion of the required number of identical copies, i.e.,

when the original is to be changed. The apparatus is relatively inexpensive and is itself uncomplicated and satisfies a long felt need for greater freedom in adjusting the variables in an electrophotographic copying machine, in addition to which it is reliable and does not involve additional complication in the setting operation.

When a number of, for example,-fairit originals are to be copied one after another, it is undesirable to have to reset the already 'set exposure each time the original is changed after a multiple copying operation has been completed. For the purpose of solving this additional problem and in accordance with the invention, a timing element may be provided which retards the actuation of the electrical release means for a period that is somewhat longer than the time required for changing the original. This timing element is so designed that it always springs back to its original position when the actuating signal for the electrical release means sent by the programming mechanism of the reproduction machine is cancelled by a fresh copying operation. In this way, it is not necessary to make an adjustment when copying originals of like contrast, but the normal exposure is nevertheless set again when the operator leaves the machine. Unintentional incorrect exposure is thus also avoided in this case.

The invention is illustrated by' way of example in the accompanying drawing, the single FIGURE of which is a perspective view of operative parts of an apparatus of the invention together with a corresponding circuit diagram.

Referring to the drawing, in an exposure device indicated generally at 2, the gap 22 between two shutter plates 16 can be increased or decreased symmetrically with respect to a center line parallel to the edges defining the gap, with the aid of a setting knob 7 through a shaft 10, meshing pinions l8 and 19 and meshing pinions 20 and 21.

Displacement of the shutter plates 16 causing a change in the width of the gap 22, brings about a change in exposure. A resetting device indicated generally at 1 re-establishes the normal exposure upon completion of a copying operation, so that originals exhibiting normal contrast are not accidentally copied in unusual exposure conditions. The mode of operation of the resetting device will now be explained.

Rotation of the setting knob 7 from its normal position indicated by the letterN causes one of two pretensioned springs 11 and 13, shown as helical springs, depending upon the direction of rotation of the shaft 10, to be further tensioned, whereas the other is relieved of load to a corresponding extent. The two springs are each connected by way of cords 23 and a pulley 24 in the case of one spring and a pulley 25 in the case of the other, to the ends of a cross-member 26 which is fixed on the shaft 10. As shown, the normal exposure can be set by the setting of a nut 27. Mounted on and rotatable with the shaft 10 is a wheel 17 which has fine teeth 8a and cmplementary recesses 8b in at least that portion of its circumference corresponding to the displacement range of the setting knob 7. The teeth engage a wire 9 across a stirrup 28. The thickness and resilience of the wire 9 are advantageously such that when the wheel 17 turns, the wire springs backwards and forwards, whereas the stirrup 28 remains in a stationary position determined by ,a stop 59 and a tension spring 31. The wire 9 is axially displaceable over a short distance in holes and is bent but not stretched when the wheel 17 turns. The length of the wire and the form of the teeth 8a are such that the springs 11 and 12, however great the deflection, cannot turn the wheel 17 back thereby overcoming the locking action of the wire 9. The stirrup 28 is firmly attached to a bar 29 which is pivoted at its upper end on a shaft 30 extending parallel to the shaft 20 of the setting knob 7. At its lower end the bar 29 is attached to the spring 31 and on its opposite side is attached to the armature 32 of an electromagnet 6, which armature is in turn pivoted in this bar. This arrangement is indicated generally at 5. Mounted on the shaft 10 of the setting knob 7 is a disc 39 of insulating material which incorporates a cam 40. Mounted on the shaft 34 of a setting knob 33 for setting the number of copies,is a further disc 35 made of insulating material which has a recess 36. Pairs of electrically conductive spring plates 37 and 38 carrying contacts 42 and 41 respectively are respectively associated with the discs 35 and 39. The spring plates 37 and 38 are mechanically so biased that in the uninfluenced condition they bring the contacts 42 and 41 into electrical contact with each other. -When the setting knob 33 is set for the required number of copies, the disc 35 separates the two contacts 42. The two contacts 41 are only separated from each other when the normal exposure has been set by means of the knob 7. In all other positions the cam 40 is not located between the contacts 41, so that these can establish electrical contact between the spring plates 38. The contacts 38/41 and 37/42 are connected in series in the circuit, indicated generally at 3, of the electromagnet 6 which is supplied with current from a source 43.

Rotation of the setting knob 33, for setting the required number of copies, causes the disc 35 to interrupt the electrical connection between the contacts 42. R- tation of the knob 7 to give stronger or weaker exposure than the normal causes the contacts 41 to come together. The wire 9 engaging the teeth 8a acts as a mechanical stop indicated generally at 4 and prevents the spring 11 or 12, tensioned as a result of rotation of the knob 7, from returning the shutter plates 16 to the position giving normal exposure.

During the course of the copying operation, a counting mechanism, not illustrated, causes the shaft 34 of the setting knob 33 to reverse through a distance corresponding to one switching position after each copy has been made. Upon completion of the copying operation the recess 36 allows the two contacts 42 to move into engagement. Since, as has been assumed above, the exposure is set to a value other than the normal, i.e., the cam 40 is not located between the contacts 41, the circuit of the electromagnet 6 is now closed. The electromagnet pulls up the armature 32 by overcoming the force of the spring 31 This causes the wire 9 to disengage from the teeth 8a, and the spring 11 or 12, tensioned as a result of rotation of the setting knob 7, can pivot the shutter plates 16 back into the position giving normal exposure. As soon as the shutter plates 16 have moved back into the normal position, the cam 40 again moves between the contacts 41 and thus interrupts the circuit of the electromagnet. The spring 31 then pulls the bar 29 back and brings the wire 9 into engagement with the teeth 8a again. This arrangement ensures that the electromagnet 6 is only energized both when the counting mechanism is zeroed and when the exposure that has been set differs from the normal. Thus during normal operation the electromagnet receives no current. The apparatus can, of course, be so designed that the electromagnet 6 presses the wire 9 against the teeth 8a of the wheel 17 and is only switched out for the resetting operation. In this case, a .pretensioned spring causes the wire 9 to disengage from the teeth.

In the drawing, a further form of electrical means for actuating the resetting mechanism isshown in broken lines. Upon completion of a copying operation, which may be a multiple one, the programming mechanism, not shown, of the production machine closes a switch 58 which always remains open at the commencement of such copying operation. This switch can be actuated for example by the relay switch of the electric motor of the machine. When this switch 58 is closed, a time delay relay 57 is set in operation and this connects'the electromagnet 6 to the current source after an interval of time which may be for example two seconds longer than that required for a normal change of original. If the copying machine is set in operation again before the expiration of this period, the switch 58 is opened, the relay 57 springs back to its initial position, and the magnet 6 is not switched in, so that no resetting of the exposure takes place.

In this way a number of originals can be copied using an exposure differing from the normal without the exposure having to be reset each time the original is changed. Accidental incorrect exposure is nevertheless avoided as far as possible, since the shutters are reset each time the operator leaves the machine.

Instead of helical springs 11 and 12 for returning the shutter plates 16, spiral springs or helical torsion springs can be used. It is also possible to reset the shutter plates with the aid of electromagnets.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodimentsare therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended 'to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

,1. In an electrophotographic reproduction machine, having a programming mechanism for single or multiple copying operations, an apparatus for adjusting the exposure, said apparatus comprising a setting device for setting the exposure, a resetting device for returning the setting device to the setting for normal exposure after it has been set at any other setting, and electrical means for actuating said resetting device in response to the end of a copying operation to return said setting device to said setting for normal exposure, said resetting device including means biasing the setting device into the setting for normal exposure, mechanical means being provided for immobilizing said setting device in its other set positions, said actuating means being adapted to release said immobilizing means, said setting device being rotatable for setting the exposure and said immobilizing means including an element movable radially with reference to the axis of rotation of said setting device to hold the setting device against rotation.

2. Apparatus according to claim 1, wherein said setting device includes a notched rotary element, said movable element of the immobilizing means comprising a resilient wire adapted to engage and catch in said notched rotary element.

3 In an electrophotographic reproduction machine, having a programming mechanism for single or multiple copying operations, an apparatus for adjusting the exposure, said apparatus comprising a setting device for setting the exposure, a resetting device for returning the setting device to the setting for normal exposure after it has been set at any other setting, and electrical means for actuating said resetting device in response to the end of a copying operation to return said setting device to said setting for normal exposure, said programming mechanism for single or multiple copying operations having an output signal for indicating the end of a copying operation, a timing device responsive to said signal for retarding said actuating means and thereby providing a predetermined time interval between the end of a copying operation and the return of said setting device to said setting for normal exposure and in which time interval an original being copied can be changed without resetting the exposure and the programming mechanism can be reset, and means responsive to the resetting of said programming mechanism for resetting said timing device.

4. In an electrophotographic reproduction machine, the apparatus comprising means for programming said machine for single or selected multiple copying operations, means for adjusting the exposure of said machine, said adjusting means including a setting device for setting the exposure, a resetting device for returning the setting device to the setting for normal exposure after it has been set at any other setting, and electrical means carried by said apparatus for actuating said resetting device in response to the end of a copying operation to return said setting device to said setting for normal exposure.

5. Apparatus according to claim 4, wherein said resetting device includes means biasing the setting device into the setting for normal exposure, mechanical means being provided for immobilizing said setting device in its other set positions, said actuating means being adapted to release said immobilizing means.

6. Apparatus according to claim 5, wherein said actuating means comprises an electromagnet device.

7. Apparatus according to claim 5, wherein said biasing means includes a spring.

8. Apparatus according to claim 5, wherein said biasing means comprises two opposed springs.

9. Apparatus according to claim 4 wherein said electrical means includes means for generating an electrical signal in response to the end of a single or selected multiple copying operation, and means coupled to said signal generating means to actuate said resetting device in response to said signal to return said setting device to said setting for normal exposure.

10. Apparatus according to claim 4 including a pair of shutter plates having a pair of edges defining a gap therebetween and mounted for movement in directions for increasing or decreasing the size of said gap, said adjusting means being connected to said shutter plates for moving said shutters to selectively increase or decrease the distance between said edges and thereby increase or decrease said gap respectively, said resetting device including means for biasing said shutters for movement within a range of positions and into a predetermined position within said range defining a selected gap size for normal exposure, means for immobilizing said shutters from movement when in positions other than said predetermined position, said actuating means being adapted to release said immobilizing means.

11. Apparatus according to claim 10 wherein said electrical means includes means for generating an electrical signal in response to the end of a single or selected multiple copying operation, means coupled to said signal generating means to actuate said resetting device in response to said signal to return said setting device to said setting for normal exposure, said electrical signal generating means including an electrical circuit having switch elements for energizing said circuit when said shutters lie in positions other than in sai predetermined position and at the end of a copying operation, said switch elements being operable to deenergize said circuit when either said shutters are moved to said predetermined position or said machine is programmed for single or multiple copying operations. 

1. In an electrophotographic reproduction machine, having a programming mechanism for single or multiple copying operations, an apparatus for adjusting the exposure, said apparatus comprising a setting device for setting the exposure, a resetting device for returning the setting device to the setting for normal exposure after it has been set at any other setting, and electrical means for actuating said resetting device in response to the end of a copying operation to return said setting device to said setting for normal exposure, said resetting device including means biasing the setting device into the setting for normal exposure, mechanical means being provided for immobilizing said setting device in its other set positions, said actuating means being adapted to release said immobilizing means, said setting device being rotatable for setting the exposure and said immobilizing means including an element movable radially with reference to the axis of rotation of said setting device to hold the setting device against rotation.
 2. Apparatus according to claim 1, wherein said setting device includes a notched rotary element, said movable element of the immobilizing means comprising a resilient wire adapted to engage and catch in said notched rotary element. 3 In an electrophotographic reproduction machine, having a programming mechanism for single or multiple copying operations, an apparatus for adjusting the exposure, said apparatus comprising a setting device for setting the exposure, a resetting device for returning the setting device to the setting for normal exposure after it has been set at any other setting, and electrical means for actuating said resetting device in response to the end of a copying operation to return said setting device to said setting for normal exposure, said programming mechanism for single or multiple copying operations having an output signal for indicating the end of a copying operation, a timing device responsive to said signal for retarding said actuating means and thereby providing a predetermined time interval between the end of a copying operation and the return of said setting device to said setting for normal exposure and in which time interval an original being copied can be changed without resetting the exposure and the programming mechanism can be reset, and means responsive to the resetting of said programming mechanism for resetting said timing device.
 4. In an electrophotographic reproduction machine, the apparatus comprising means for programming said machine for single or selected multiple copying operations, means for adjusting the exposure of said machine, said adjusting means including a setting device for setting the exposure, a resetting device for returning the setting device to the setting for normal exposure after it has been set at any other setting, and electrical means carried by said apparatus fOr actuating said resetting device in response to the end of a copying operation to return said setting device to said setting for normal exposure.
 5. Apparatus according to claim 4, wherein said resetting device includes means biasing the setting device into the setting for normal exposure, mechanical means being provided for immobilizing said setting device in its other set positions, said actuating means being adapted to release said immobilizing means.
 6. Apparatus according to claim 5, wherein said actuating means comprises an electromagnet device.
 7. Apparatus according to claim 5, wherein said biasing means includes a spring.
 8. Apparatus according to claim 5, wherein said biasing means comprises two opposed springs.
 9. Apparatus according to claim 4 wherein said electrical means includes means for generating an electrical signal in response to the end of a single or selected multiple copying operation, and means coupled to said signal generating means to actuate said resetting device in response to said signal to return said setting device to said setting for normal exposure.
 10. Apparatus according to claim 4 including a pair of shutter plates having a pair of edges defining a gap therebetween and mounted for movement in directions for increasing or decreasing the size of said gap, said adjusting means being connected to said shutter plates for moving said shutters to selectively increase or decrease the distance between said edges and thereby increase or decrease said gap respectively, said resetting device including means for biasing said shutters for movement within a range of positions and into a predetermined position within said range defining a selected gap size for normal exposure, means for immobilizing said shutters from movement when in positions other than said predetermined position, said actuating means being adapted to release said immobilizing means.
 11. Apparatus according to claim 10 wherein said electrical means includes means for generating an electrical signal in response to the end of a single or selected multiple copying operation, means coupled to said signal generating means to actuate said resetting device in response to said signal to return said setting device to said setting for normal exposure, said electrical signal generating means including an electrical circuit having switch elements for energizing said circuit when said shutters lie in positions other than in sai predetermined position and at the end of a copying operation, said switch elements being operable to de-energize said circuit when either said shutters are moved to said predetermined position or said machine is programmed for single or multiple copying operations. 